Religion being a comfort is no excuse. Don't you want your daughter to have freedom over what she believes? Don't you want her to understand the world as it IS, rather than as some delusional people say it is?
Why do you believe she should ha\ve no privacy?
btw what do you think your answers would be if she wasn't 9/10 mentally?
Unless she is exposed to religion she will not have the freedom over what she believes. She hasn't been exposed to Bhuddism, Judiasm, Shintoism, Voodoo, etc. We chose to let her be taught my husband's religion.
Since she cannot always express what she wants to say fully I use the clues I find to help me guide conversations with her.
If she were able to function on an older level I would probably say that when she reached high school she could decide on whether to continue church. Privacy would continue to be at my discretion until she left for college.
BTW, a dear friend has a daughter the Princess Royal's age with similar problems. This girl had brain surgery to reduce epileptic seizures. Unfortunately when the surgery was performed they removed part of her impulse control. Every time they leave a store the mom pats the daughter down and returns any items to the shelves. Also her room is examined every so often and missing things returned to school or church as appropriate. No privacy there either.